Lab 2

Macromolecules of Life
Hands-On Labs, Inc. Version 42-0085-00-01

Lab Report Assistant

________________
Name: Akil Kelly
Exercise 1: Testing for Proteins

Data Table 1: Biuret results.
Substance Tested
Predicted Results
Biuret Color & Number of drops added
1: Egg white Contains Protein Purple color – 9 drops
2: Pepsin Contains Protein Purple color – 9 drops
3: Sugar Doesn't contain protein Blue color – 9 drops
4: Distilled water Doesn't contain protein Blue color – 9 drops

Which substances tested contain protein and which do not? How do you know?
Egg white and pepsin contained protein as indicated by the appearance of a purple color in solution, whereas sugar and distilled water did not, as indicated by no color change from the blue biuret reagent.

Questions

A. Which of the test tubes are the positive and negative controls?
The experiment illustrated that:
The Positive controls were Test tube #1 Egg white and #2 Pepsin.
The Negative controls were Test tube #4 Distilled water and #3 Sugar.

B. What conclusions can be made about this experiment?
The experiment concluded that proteins can be found in enzymes such as pepsin and animal products such as egg whites, but absent in carbs such as sugar and neutral solutions such as water.

C. How might Biuret reagent be used in a practical real-life situation?
It could be used to determine the presence of protein in urine indicating kidney damage.

D. How did the predicted results compare to the actual results?
The predicted results and the actual results were the same.

Exercise 2: Testing for Sugars
Observations

Data Table 2: Benedict’s Reagent Results.
Test Sample
Predicted Results
Benedict’s results
#1 Glucose Contains sugars Red
#2 Starch Contains sugars Blue
# 3 Onion juice Does not contain sugars Orange
#4 Distilled Water Does not contain sugars Blue

Which substances tested contain sugars and which do not? How do you know?
In order to determine whether each substance contained sugar, their color changes were compared to the Benedict’s reagent scale. Glucose and onion juice contained sugars as indicated by the appearance of a red color after adding Biuret reagent.

Questions

A. Which of the test tubes are used as the positive and negative controls?
The experiment determined that Test tube # 1 Glucose was the positive control and Test tube #4 was the negative control.

B. How did the predicted results compare to the actual results?
The predictions for test tubes #4 and #1 match the results however the predictions for the other two test tubes do not.

C. What can be concluded from this experiment?

The experiment concluded that Test tube#1 Glucose contains the most sugars, as indicated by the bold red color on Benedict’s reagent scale for increasing amounts of simple sugars.

D. How might Benedict’s reagent test be used in a practical real-life situation?
It can be used to test ones urine for traces of sugar, which can inform one of diabetic issues.

Exercise 3: Testing for Starch
Observations

A. Write a hypothesis about whether a potato or onion has the most starch.
If the starch content of a potato and an onion is tested, the amount of starch would be higher in the potato

Observations Table: Exercise 3
A. View of potato under pocket microscope. Magnification = 200x At this point of magnification the cellulose walls of the potato are quite evident and appears to be packed tightly together.
B. View of potato cells with IKI. Magnification = 200x At this point of magnification with IKI the cell walls appear also packed together. The darkness is a positive indicator of the iodine solution, illustrates the presence of starch in the cells.

Observations Table: Exercise 3
A. View of onion cells without IKI. Magnification =160x At this point of magnification the Onion illustrates the brick like array of the onion’s cells.
B. View of onion cells with IKI. Magnification = 160x Here the onion cells have barely changed color that indicates that there is some starch but a significant lower level compared to the Potato.

Questions

A. Which vegetable has the most starch?
Potatoes

B. What is the purpose of starch in vegetables? Hint: What is the function of stored sugar?

It is converted to sugar to be used as energy.

B. How might the IKI reagent test be used in a practical real-life situation?
Starch grains are found in the chloroplast of plants, The IKI reagent test can be used to test if plant leaves are deprived of sunlight since starch forms in chloroplast that is exposed to light.

C. Did the results differ from your hypothesis? Explain.
The hypothesis and the experiment results yielded the same results.

Exercise 4: Testing for Lipids
Observations

Data Table 3: Lipid test results.
Macromolecule Being
Tested
Hypothesis: contain lipid or not
Results from test
Potato
Does not contain lipid No Lipid
Onion
Does not contain lipid No Lipid
Oil
Contains lipid Lipid dH2O Does not contain lipid No lipid

Which substances tested contain lipids and which do not? How do you know?
Oil contained lipids as indicated by the red-ish stain from the Sudan Red test.

Questions

A. What is the test substance?
Lipids

B. Which test represents the control?
The distilled water represents the control, as it is common knowledge distilled water does not contain lipids.

C. Which test contained the most test substance?
The experiment illustrated that Oil has a significantly higher amount of lipids of the group, as it extended beyond the marked boundaries of the Sudan III drop.

D. Did the results agree with the initial hypothesis in every case? Explain why or not.
The hypothesis and experiment results yielded the same results. Oil was expected to contain Lipids because it is a high source of fat.

**You do not need to perform Exercise 5: Making Mayonnaise**

Conclusions

A. What classes of compounds are present in living organisms that are not tested for in this exercise?
Nucleic aids

Please attach photographs of the experiment set up of each exercise here (#1-4)

Experiment #1

Figure 1: Experiment 1

Figure 2: Experiment #2

Figure 3: Experiment #3